# Voltage Regulator heat sink vs two voltage regulators

#### sirchuck

Joined Feb 14, 2016
150
Generally everyone talks about just adding a heat sink to a voltage regulator or power transistor, and of course that makes sense. But I'm curious, would adding an additional voltage regulator also limit the heat produced by either regulator?

Imagine you have a 12v power supply run through a 6v regulator, and then through a 3v regulator. It seems to me that should divide up the excess heat between the two regulators. Maybe it wouldn't be as efficient as a heat sink, but it seems sensible this could eliminate the need for a heat sink in some circuits by keeping each component cooler in the first place.

#### Alec_t

Joined Sep 17, 2013
13,776
The two regs would share the heat. If, for example, you drew the same current A from each regulator, one would be dissipating (12-6) x A = 6AWatts and the other (6-3) x A = 3A Watts.

#### dl324

Joined Mar 30, 2015
15,818
It depends. If the 6V regulator was being operated near it's limits, adding the 3V regulator's load to it wouldn't make sense. If the 3V regulator's load is sufficiently small, it wouldn't make much difference if the input was 12V or 6V.

#### sirchuck

Joined Feb 14, 2016
150
It depends. If the 6V regulator was being operated near it's limits, adding the 3V regulator's load to it wouldn't make sense. If the 3V regulator's load is sufficiently small, it wouldn't make much difference if the input was 12V or 6V.
Ok, that sound contrary to what Alec_t said, but I think I kind of see what you are saying.
Assume 12v power supply and 1amp of current, and if we should use a heat sink at anything over 1 watt of power.

6v Regulator:
( 12v - 6v ) * 1a = 6w : Heat sink needed

3v Regulator:
( 6v - 3v ) * 1a = 3w : Heat sink needed

So adding the second regulator did nothing to help the 6v regulator, if I did the math right and if I understood you, I just added unnecessary components.

Edit:
If the 6v regulator wasn't there though:
(12v - 3v) * 1a = 9w : Heat sink needed

So now I guess, while I still need a heat sink, I will actually generate less heat for my lowest regulator in the chain. Multiple regulators may still be a useful thing.

#### dl324

Joined Mar 30, 2015
15,818
Having the regulators in series would add the 3V regulator's current to the 6V, so the 6V regulator would draw 2A and dissipate 12W. The 3V regulator would dissipate 3W, so total dissipation in regulators would be 15W.

#### crutschow

Joined Mar 14, 2008
32,859
The only way to eliminate the heat sink would be to have enough regulators so they each is dissipating no more than its free air rating. Typically that's no more than a watt or so.

#### sirchuck

Joined Feb 14, 2016
150
The only way to eliminate the heat sink would be to have enough regulators so they each is dissipating no more than its free air rating. Typically that's no more than a watt or so.
That's the way I initially thought about it, but from what I understood about what DL324 said, more components would increase the amp draw for the higher regulators in the series chain, causing an overall higher watt output. The top regulator would produce even more heat because of the amps drawn from the lower regulators. (feel free to correct me)

Adding more regulators would (from what I understood) just cause the top regulator to run even hotter, so a heat sink is a better option.

There may be other/better heat reducing solutions like using a voltage divider resistor circuit, then adding your regulator, but sticking to heatsinks vs regulators, it seems the heatsinks are the only solution to keep the first regulator cool.

#### hp1729

Joined Nov 23, 2015
2,304
Putting regulators in series doesn't take the load off of voltage regulators higher up the line. Separate voltage regulators works if you trim the voltage so they are equal. But what is so wrong with heat sinks?
I have seen people use the aluminum head off of a motorcycle engine used as a heat sink. (Mr. Robert Pease of all people I think it was.)
I know is seems ridiculous to spend more for a heat sink than the regulator cost, but most any chunk of aluminum can be used as a heat sink.

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